Enabling IMS services for non-IMS UEs via a home base station subsystem

ABSTRACT

Apparatuses and methods for enabling IMS services for non-IMS UEs via a home base station subsystem are described. In various embodiments, a home base station subsystem includes a message generator configured to generate an Internet Protocol multimedia subscription request message comprising a unique user identifier and an information request message, the information request message requesting an Internet Protocol multimedia subscription for the user identified by the unique user identifier. The home base station subsystem also includes a transmitter configured to transmit the generated Internet Protocol multimedia subscription request message to a user database.

BACKGROUND

Various embodiments relate generally to communication technologies, andin particular, to a technology for a non-IP Multimedia Subsystem (IMS)user to access an IMS network.

The Public Land Mobile Network (PLMN) defined by the 3rd GenerationPartnership Project (3GPP) can be logically divided into two parts: aCore Network (CN) and an Access Network (AN). The CN can be subdividedinto a Circuit Switched (CS) domain, a Packet Switched (PS) domain, andan IP Multimedia Subsystem (IMS).

In the CS domain, the Mobile Switching Center (MSC) handles severalmobility and routing dependant functions for CS-based services. The mainCS-based service is a voice call.

In the PS domain, a Serving GPRS Support Node (SGSN) handles severalmobility and routing dependant functions needed for PS-based services.The SGSN is connected to a Gateway GPRS Support Node (GGSN), which isconfigured to offer access to the IMS. A network is conventionallyorganized so that the MSC, GGSN, and SGSN are connected to the HLR (HomeLocation Register). The HLR stores all subscriber specific data.

In the CS-Domain, the control of connections (e.g., reserving datatransfer means) and calls (e.g., calling, negotiation of codecs,hang-up) are both done on the MSC. For example, after a successfulestablishment of a call, the MSC routes the voice data towards thenetwork.

In the PS-domain, there is a division of duties between the control ofconnections (e.g., reserving network layer addresses or IP-addresses andmeans for PS-data transfer), otherwise known as “sessions” and thecontrol of application layer services (e.g., voice calls with voicecodec, data rate, required QoS). The SGSN controls sessions in additionto routing voice-data after successful establishment of a session. TheIMS controls application layer services. For example, the IMS definesmeans to request and negotiate services and their parameters on anapplication layer between a UE and the connection endpoint. The IMS alsorelies on the core-network to setup and maintain the appropriatesessions via transferring the associated data through the network to theUE.

One feature of a conventional network, is the ability to update aposition status of a UE (User Equipment) that has changed locations. Ina conventional network, a UE in Idle Mode performs cell-selectionautonomously and thus the network is not aware which cell the UE iscurrently located. The network is only aware of the Location Area (LA)which is in general an area spanned by a number of mobile radio cells.In case of network triggered connection setup is required the networkpages the UE in all mobile radio cells of the LA that the UE iscurrently registered in. Each mobile radio cell indicates the LA whereit belongs to by transmitting a Location Area Identity (LAI).

A conventional location update procedure for the CS domain user is shownin FIG. 1. More specifically, FIG. 1 shows a location update procedurethat includes changing both the LA and MSC. Although the relationbetween MSCs and LA is a choice of the network operator, the locationupdate procedure of FIG. 1 includes changing both the LA and MSC for aclear presentation of the location areas update procedure.

Prior to UE 102 moving from the cell of NodeB 106 to the cell of NodeB116, UE 102 is registered at the LA of the cell of NodeB 106 and RNC 107and obtained a TMSI from MSC 108. UE 102 has also stored the LocationArea Identity (LAI) broadcasted by NodeB 106. At Step 1, UE 102, in idlemode, moves to the cell of NodeB 116. NodeB 116 transmits a differentLAI than NodeB 106. Thus, a location update is initiated.

That is, when UE 102 moves from the cell of NodeB 106 to the cell ofNodeB 116, UE 102 reads a LAI from the system information transmitted byNodeB 116. Because the LAI transmitted by NodeB 116 is different fromthe LAI received from NodeB 106 and stored in UE 102, UE 102 initiates alocation update at Step 2 by transmitting a location updating requestmessage towards NodeB 116 and Radio Network Controller (RNC) 120 of MSC122. The location updating request message includes the Temporary MobileSubscriber Identity (TMSI) assigned by NodeB 106 and the LAI of NodeB106. An acknowledge message, which indicates the successfulestablishment of the radio resource connection, is transmitted back toUE 102 at 118.

The now “new” MSC 122 detects that the received LAI is different fromits own LAI. At Step 3, MSC 122 thus uses the LAI received from UE 102to obtain the address of MSC 108 and transmits a send parameters messageto the MSC 108. A send parameters message also includes the TMSI sent toMSC 122 by UE 102. MSC 108 responds by sending the International MobileSubscriber Identity (IMSI) that corresponds to the received TMSI useridentity back to MSC 122.

At Step 4, MSC 122 sends an Update Location message to HLR 128. TheUpdate Location message includes the IMSI of UE 102 and the address ofMSC 122. HLR 128 updates the record for UE 102 with the receivedparameters and sends an Insert Subscriber Data message back to MSC 122.The message includes security credentials for UE 102. MSC 122 creates arecord for UE 102 and transmits an Insert Subscriber Data Result messageto HLR 128 to indicate the successful creation of the data record in MSC122.

At Step 5, HLR 128 transmits a Cancel Location message to MSC 108. MSC108 deletes the record associated with UE 102 and transmits a CancelLocation Result message back to HLR 128. HLR 128 transmits to MSC 122 anUpdate Location Result message indicating a successful location updatein HLR 128.

At step 6, MSC 122 initiates the authenticating process for UE 102 bytransmitting to UE 102 an authentication request message, which includesa security challenge. UE 102 verifies, based on the authenticationrequest message, that the request is trustful and computes a result tothe challenge. UE 102 then transmits the result back to MSC 122. MSC 122compares the result with the stored data earlier obtained from HLR 128.If the result matches, UE 102 is authenticated.

At Step 7, MSC 122 initiates ciphering for the connection towards UE 102by transmitting a Ciphering Mode Command message to RNC 120, whichforwards the message to UE 102. UE 102 switches to cipher mode andtransmits a Ciphering Mode Complete message to RNC 120, which forwardsthe message to MSC 122.

At Step 8, MSC 122 assigns a TMSI to UE 102 and transmits the TMSI withthe message Location Updating Accept to UE 102. UE 102 starts using thisTMSI and transmits the TMSI Reallocation Complete message back to MSC122. This indicates the successful completion of the location updatingprocedure.

After successful completion of the location update procedure, thenetwork is aware of the new location area of UE 102, MSC 122 hasobtained required subscriber data, and UE 102 has obtained a newtemporary ID, a TMSI.

The above procedure shown in FIG. 1 only allows UE 102 to use CS-domainnetwork resources of a Core Network. Using conventional techniques, UE102 must initiate a GPRS attach procedure in order to obtain servicesfrom the PS-domain.

A conventional GPRS attach procedure and associated message exchangesare illustrated in FIG. 2.

At Step 1, UE 102 is either switched on or is otherwise not attached tothe PS-Domain. At Step 2, UE 102 transmits an Attach Request messagetowards NodeB 114. The message is forwarded to RNC 120 and SGSN 122 andincludes the RAI and the currently assigned P-TMSI or if a P-TMSI is notavailable, an IMSI.

At Step 3 a, SGSN 122 transmits an Identification Request message toSGSN 108 by using the RAI previously received by UE 102. The messagealso includes in the P-TIMSI. SGSN 108 responds by sending aidentification response message back to SGSN 122. The message includesthe IMSI and security credentials.

At Step 3 b, SGSN 122 sends a Send Authentication Info message, whichincludes the IMSI, to HLR 128. HLR 128 sends a Send Authentication InfoACK message, which includes the security credentials, back to SGSN 122.SGSN 122 initiates the authentication procedure for UE 102 bytransmitting to UE 102 an Authentication and Ciphering Request message,which includes a security challenge. UE 102 verifies, based on theauthentication request message, that the request is trustful andcomputes a result to the challenge. UE 102 then transmits the resultback to SGSN 122 with an Authentication and Ciphering Response message.SGSN 122 compares the result computed by UE 102 with the stored dataobtained from HLR 128, and if the result matches, UE 102 isauthenticated.

At Step 4, SGSN 122 transmits an Update Location message, which includesthe IMSI and new RAI, to HLR 128. HLR 128 updates the record for UE 102with the received parameters and sends an Update Location ACK messageback to SGSN 122.

At Step 5, SGSN 122 assigns a TMSI to UE 102 and transmits the messageAttach Accept with the TMSI to UE 102. UE 102 utilizes the received TMSIand transmits an Attach Complete message back to SGSN 122. The messageindicates the successful completion of the GPRS attach procedure.

The procedures of FIG. 1 and FIG. 2 only allow UE 102 to use CS domainand PS domain network resources of a Core Network. In order to useIMS-based services, UE 102 has to register in the IMS. Severalrequirements are defined for UEs to be able to register in the IMS, oneof which is the presence of an IMS Subscriber Identity Module (ISIM). Inthe early phases of implementing IMS, it is expected that many UEscannot fulfill these requirements, including UEs that do not have orcannot support an ISIM. To enable access to IMS by non-IMS compliantUEs, the GPRS-IMS Bundled Authentication (GIBA) procedure is defined.The procedure can be used by UEs which are using the PS domain to accessthe IMS.

A conventional GPRS-IMS Bundled Authentication procedure and messageexchanges are illustrated in FIG. 3.

Four network elements are relevant in the IMS:

Proxy Call Session Control Function (P-CSCF) 130 is the first contactpoint within the IMS and behaves like a Proxy, i.e. it accepts requestsand services them internally or forwards them on.

Interrogating CSCF (I-CSCF) 132 is the contact point within anoperator's network for all connections destined to a user of thatnetwork Operator, or a roaming user currently located within thatnetwork operator's service area.

Serving CSCF (S-CSCF) 134 performs the session control services for aUE. S-CSCF 134 maintains a session state as needed by the networkoperator for support of services.

The Home Subscriber Server (HSS) 136 is a subscriber database similar toan HLR, but with enhanced authentication, authorization, and accountingfunctionality.

At Step 1, UE 102 transmits an Activate PDPD Context Request message toSGSN 122 via NodeB 114 and RNC 120. The message establishes acommunication link between GGSN 138 and UE 102. UE 102 then transmits aCreate PDPD Context Request message to GGSN 138. A PDP address (e.g., anIP Address) is assigned by SGSN 122, GGSN 138, or by an external PacketData Network. An Accounting Request Start Request message, whichincludes an assigned PDP address, MSISDN, and IMSI, is then transmittedto the HSS 136. HSS 136 stores the relation between the transmitted dataand transmits an Accounting Request Start Answer message to GGSN 138,which also stores the relation between the data. GGSN 138 then transmitsa Create PDP Context Response message to SGSN 122. SGSN 122 transmits anActivate PDPD Context Accept message, which includes the assigned PDPaddress, to UE 102.

At Step 2, UE 102 transmits an SIP Register message, which includes theassigned PDP address and the IMS Public User Identity (IMPU), to GGSN138. GGSN 138 checks whether the PDP address is correct (e.g. it is notspoofed). If the PDPD address is correct, GGSN 138 forwards the messageto P-CSCF 130. P-CSCF 130 checks the source IP address against the SIP“via” field, and if both are the same, P-CSCF 130 forwards the messageto I-CSCF 132. I-CSCF 132 transmits a User Authentication Requestmessage, which includes the IMPU, to HSS 136. HSS 136 acknowledges theauthentication to I-CSCF 132 with the message User AuthenticationAnswer.

At Step 3, I-CSCF 132 sends the SIP Register message to S-CSCF 134. Thistriggers S-CSCF 134 to transmit to HSS 136 the messageMultimedia-Auth-Request, which includes the IMPU and an indication thatGIBA is being used. HSS 136 maps IMPU to the IMSI or MSISDN of UE 102and reads the stored IP address for UE 102. HSS 136 then transmits aMultimedia-Auth-Answer message, which includes the stored IP-Address,back to S-CSCF 134. S-CSCF 134 checks the received IP-Address with theIP-Address received from I-CSCF 132. If the received IP-Addresses arethe same, S-CSCF 134 transmits a Server-Assignment-Request message toHSS 136. HSS 136 stores the received data and transmits aServer-Assignment-Answer back to S-CSCF 134.

At Step 4, S-CSCF 134 completes the GPRS-IMS Bundled Authenticationprocedure by transmitting an SIP 200 OK message back to UE 102.

The GPRS-IMS Bundled Authentication procedure shown in FIG. 3 requiresintegrating the data of a HLR into the HSS so that the HSS can registera legacy UE with a USIM and thus use the resources of the IMS. Such anapproach requires replacing the conventional HLRs or overlying one ormore special HSSes for providing IMS services on the conventionalnetworks while the conventional HLRs remain unchanged to provide the CSand PS domain services.

Solutions under discussion by the Third Generation Partnership Project(3GPP) include using a Home Node B (HNB) and Home Node B-Gateway(HNB-GW) for access to the PS-Domain and IMS for voice services andrequire a connection between the HNB Subsystem and an MSC. This isunfavorable as the HNB Subsystem and MSC connection requires theoperator providing additional signaling and network resources.

In addition, such a solution requires deriving the IMS subscriptionneeded for IMS registration from the UE address used in the 3G corenetwork, such as IMSI derived IMPU. In implementing the IMSI derivedIMPU, the network element responsible for IMS registration generates theIMPU by using the IMSI of the relating UE (e.g.2483235551234@323.248.imsi.3gppnetwork.org). Thus, HLRs or HSSes need tobe configured to accept the IMS Registration from all UEs that have avalid IMSI. This requires the HLR/HSS to generate and maintain largenumbers of related subscriber records.

Other solutions include an IMS client in the HNB. This requires storingthe IMSI of the UE in the HNB in order to perform IMS registration. Itis preferred, though, to keep the IMSI protected and therefore not totransmit it un-ciphered over the air to an HNB or store it in anun-secure location such as an HNB.

SUMMARY

Embodiments provide a home base station subsystem that includes amessage generator configured to generate an Internet Protocol multimediasubscription request message comprising a unique user identifier and aninformation request message, the information request message requestingan Internet Protocol multimedia subscription for the user identified bythe unique user identifier. The home base station subsystem alsoincludes a transmitter configured to transmit the generated InternetProtocol multimedia subscription request message to a user database.

Embodiments further provide a user database system that includes areceiver configured to receive an Internet Protocol multimediasubscription request message comprising a unique user identifier and aninformation request message, the information request message requestingan Internet Protocol multimedia subscription for the user identified bythe unique user identifier. The user database system further includes anInternet Protocol multimedia subscription generator configured togenerate an Internet Protocol multimedia subscription for the useridentified by the unique user identifier in the received InternetProtocol multimedia subscription request message. The user databasesystem further includes a transmitter configured to transmit theInternet Protocol multimedia subscription to a home base stationsubsystem.

Embodiments further provide a home base station subsystem that includesa receiver configured to receive a circuit-switched based mobilitymanagement message and a message generator configured to generate apacket-switched based attach request message to attach to apacket-switched domain.

A home base station subsystem that includes a circuit-switched receiverconfigured to receive a circuit-switched based message comprising a useridentifier and a packet-switched based message generator configured togenerate a packet-switched based message to request security-relatedinformation associated with the received user identifier. The home basestation subsystem further includes a packet-switched based receiverconfigured to receive a packet-switched based authentication requestmessage and a circuit-switched based message generator configured togenerate a circuit-switched based message to request authentication of acommunication device associated with the user identified by the useridentifier, upon receipt of the packet-switched based authenticationrequest message. The home base station subsystem further includes acircuit-switched transmitter to transmit the circuit-switched basedmessage to the communication device.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, like reference characters generally refer to the sameparts throughout the different views. The drawings are not necessarilyto scale, emphasis instead generally being placed upon illustrating theprinciples of embodiments. In the following description, variousembodiments are described with reference to the following drawings, inwhich:

FIG. 1 shows a conventional location update procedure for a CS UE;

FIG. 2 shows a conventional GPRS attach procedure and associated messageexchanges;

FIG. 3 shows a conventional GPRS-IMS Bundled Authentication procedureand message exchanges;

FIG. 4 shows a communication network according to an embodiment.

FIG. 5 shows a message sequence chart of a circuit switch user equipmentaccessing an IP Multimedia Subsystem network via a Home Node Subsystemaccording to an embodiment;

FIGS. 6A and 6B show a message sequence chart and network map of acircuit switch user equipment accessing an IP Multimedia Subsystemnetwork via a Home Node Subsystem according to an embodiment;

FIGS. 7A-7D show communication methods according to embodiments; and

FIG. 8 shows block diagrams of an architecture for a HNB according to anembodiment.

DESCRIPTION

The following detailed description refers to the accompanying drawingsthat show, by way of illustration, specific details and embodiments inwhich the invention may be practiced. These embodiments are described insufficient detail to enable those skilled in the art to practice theinvention. Other embodiments may be utilized and structural, logical,and electrical changes may be made without departing from the scope ofthe invention. The various embodiments are not necessarily mutuallyexclusive, as some embodiments can be combined with one or more otherembodiments to form new embodiments.

The following embodiments will be disclosed on the basis of a datacommunication relationship between a Home Node B Subsystem (HNBS)comprising a femtocell and a HNB-GW and a mobile radio communicationterminal device, such as e.g. a user equipment (UE). In this case, afemtocell is used as a node of a mobile radio communication network andcan directly communicate with a UE.

The term “HNBS” may include a femtocell, HNB, HeNB, a HNB-GW and/or anynetwork element that may be placed in between a HNB and HNB-GW.

The term “Home Location Register/Home Subscriber Server” (HLR/HSS) mayinclude a modified HLR or HSS.

The term “femtocell” may be replaced with access point base station,Home Node B (HNB), or Home eNodeB B (HeNB). The term “Home eNodeB”(HeNB) is used for the radio access technologies (RAT) OFDMA/SC-FDMAaccording to LTE. The term “Home Node B” (HNB) is used for the radioaccess technology (RAT) W-CDMA.

In various embodiments, a ‘Home NodeB’ may be understood in accordancewith 3GPP as a trimmed-down version of a cellular mobile radio basestation optimized for use in residential or corporate environments(e.g., private homes, public restaurants or small office areas). Invarious examples throughout this description, the terms ‘Home BaseStation’, ‘Home NodeB’, ‘Home eNodeB’, and ‘Femtocell’ are referring tothe same logical entity and will be used interchangeably throughout theentire description.

The so-called ‘Home Base Station’ concept shall support receiving andinitiating cellular calls at home, and uses a broadband connection(typically DSL, cable modem or fiber optics) to carry traffic to theoperator's core network bypassing the macro network architecture(including legacy NodeBs or E-NodeBs, respectively), i.e. the legacyUTRAN or E-UTRAN, respectively. Femto Cells shall operate with allexisting and future handsets rather than requiring customers to upgradeto expensive dual-mode handsets or UMA devices.

From the customer's perspective, ‘Home NodeBs’ offer the user a singlemobile handset with a built-in personal phonebook for all calls, whetherat home or elsewhere. Furthermore, for the user, there is only onecontract and one bill. Yet another effect of providing ‘Home NodeBs’ maybe seen in the improved indoor network coverage as well as in theincreased traffic throughput. Moreover, power consumption may be reducedas the radio link quality between a handset and a ‘Home Base Station’may be expected to be much better than the link between a handset andlegacy ‘NodeB’.

In an embodiment, access to a ‘Home NodeB’ may be allowed for a closeduser group only, i.e. the communication service offering may berestricted to employees of a particular company or family members, ingeneral, to the members of the closed user group. This kind of ‘HomeBase Stations’ may be referred to as ‘Closed Subscriber Group Cells’(CSG Cells) in 3GPP. A mobile radio cell which indicates being a CSGCell may need to provide its CSG Identity to the mobile radiocommunication terminal devices (e.g. the UEs). Such a mobile radio cellmay only be suitable for a mobile radio communication terminal device ifits CSG Identity is e.g. listed in the mobile radio communicationterminal device's CSG white list (a list of CSG Identities maintained inthe mobile radio communication terminal device or in an associated smartcard indicating the mobile radio cells which a particular mobile radiocommunication terminal device is allowed to use for communication). Invarious embodiments, a home base station may be a consumer device thatis connected to the mobile radio core network via fixed line (e.g. DSL)or wireless to a mobile radio macro cell. It may provide access tolegacy mobile devices and increase the coverage in buildings and thebandwidth per user. In various embodiments, a home base station may berun in open or closed mode. In closed mode the home base station mayprovide access to a so-called closed subscriber group (CSG) only.Examples for such closed subscriber groups are families or some or allemployees of a company, for example.

As a ‘Femto Cell’ entity or ‘Home Base Station’ entity will usually be abox of small size and physically under control of the user, in otherwords, out of the MNO's domain, it could be used nomadically, i.e. theuser may decide to operate it in his apartment, but also in a hotel whenhe is away from home, e.g. as a business traveler. Additionally a ‘HomeNodeB’ may be operated only temporarily, i.e. it can be switched on andoff from time to time, e.g. because the user does not want to operate itover night or when he leaves his apartment.

The term “user equipment” may be replaced with mobile radiocommunication terminal device (MCD), mobile phone, or terminal device.The term “legacy UE” may include UEs which are able to operate asspecified for Release 7 of UMTS and/or other non-IMS UEs not able todirectly establish a connection with the IMS.

FIG. 4 shows communication network 400 according to according to anembodiment. In some embodiments, messages between HNB 402 and SGSN 404are based on GPRS Mobility Management (GMM) messages. In someembodiments, messages between HNB 402 and UE 406 are based on MobilityManagement (MM) messages. HNB 402 converts the protocols/messages. Forexample, the GMM message Authentication and Ciphering Request from SGSN404 is converted into the MM message Authentication Request and sent toUE 406. Another example is the MM message Authentication Response fromUE 406 is converted into the GMM message Authentication and CipheringResponse and sent to SGSN 404. As a result, the authenticationparameters A UTN and RAND are forwarded by the HNB 402 to UE 406 withoutchange and the Authentication Response Parameter is also forwarded byHNB 402 to SGSN 404 without change.

HNB 402 may transmit date of the lower protocol layers to HNB-GW 410over IP network 408. In alternative embodiments, HNB-GW 410 may performthe GMM to MM conversion functions.

The content of the above messages are described in the tables below:

TABLE 1 AUTHENTICATION AND CIPHERING REQUEST MESSAGE CONTENT IEIInformation Element Type/Reference Presence Format Length Protocoldiscriminator Protocol discriminator M V ½ 10.2 Skip indicator Skipindicator M V ½ 10.3.1 Authentication and ciphering Message type M V  1request message identity 10.4 Ciphering algorithm Ciphering algorithm MV ½ 10.5.5.3 IMEISV request IMEISV request M V ½ 10.5.5.10 Force tostandby Force to standby M V ½ 10.5.5.7 Authentication and ciphering A&Creference number M V ½ reference number 10.5.5.19 21 Authenticationparameter RAND Authentication parameter RAND O TV 17 10.5.3.1  8- GPRSciphering key sequence Ciphering key sequence number C TV  1 number10.5.1.2 28 Authentication parameter Authentication parameter AUTN O TLV18 AUTN 10.5.3.1.1

TABLE 2 AUTHENTICATION REQUEST MESSAGE CONTENT IEI Information elementType/Reference Presence Format Length Mobility management Protocoldiscriminator M V ½ protocol discriminator 10.2 Skip Indicator SkipIndicator M V ½ 10.3.1 Authentication Request Message type M V  1message type 10.4 Ciphering key sequence Ciphering key sequence M V ½number number 10.5.1.2 Spare half octet Spare half octet M V ½ 10.5.1.8Authentication Auth. parameter RAND M V 16 parameter RAND (UMTS 10.5.3.1challenge or GSM challenge) 20 Authentication Auth. parameter AUTN O TLV18 Parameter AUTN 10.5.3.1.1

TABLE 3 AUTHENTICATION RESPONSE MESSAGE CONTENT IEI Information elementType/Reference Presence Format Length Mobility management Protocoldiscriminator M V ½ protocol discriminator 10.2 Skip Indicator SkipIndicator M V ½ 10.3.1 Authentication Response Message type M V 1message type 10.4 Authentication Response Auth. Response parameter M V 4parameter 10.5.3.2 21 Authentication Response Auth. Response parameter OTLV 3-14 Parameter (extension) 10.5.3.2.1

TABLE 4 AUTHENTICATION AND CIPHERING RESPONSE MESSAGE CONTENT IEIInformation Element Type/Reference Presence Format Length Protocoldiscriminator Protocol discriminator M V ½ 10.2 Skip indicator Skipindicator M V ½ 10.3.1 Authentication and ciphering GPRS message type MV 1 response message identity 10.4 A&C reference number A&C referencenumber M V ½ 10.5.5.19 Spare half octet Spare half octet M V ½ 10.5.1.822 Authentication parameter Authentication Response parameter O TV 5Response 10.5.3.2 23 IMEISV Mobile identity O TLV 11  10.5.1.4 29Authentication Response Authentication Response parameter O TLV 3-14parameter (extension) 10.5.3.2.1

FIG. 5 shows a message sequence chart of a circuit switch user equipmentaccessing an IP Multimedia Subsystem network via a Home Node Subsystemaccording to an embodiment.

At Step 0, Legacy UE, for example a UE based on UMTS Release 7, sends alocation update message to HNBS in order for the Legacy UE to connect tothe inventive HNBS. The location update message triggers the HNBS toperform the following steps:

At Step 1, the HNBS requests the SGSN for a P-TMSI and securitycredentials for the Legacy UE. The SGSN retrieves the IMSI from the MSCand stores the relation between IMSI and P-TMSI. This aspect of theprocedure may have the effect that it removes from the MSC the signalingload for mobility management.

At Step 2, SGSN sends and HNBS derives the P-TMSI and the securitycredentials needed for ciphering data towards the Legacy UE. This aspectof the procedure may have the effect that no connection between the HNBSand a MSC is required.

At Step 3, HNBS forwards authentication information between the corenetwork and the Legacy UE by converting CS-based and PS-based transportprotocols. The IMSI is not transmitted to the HNBS. This aspect of theprocedure may have the effect that the IMSI is secure in the network andnot accessible through the potentially vulnerable HNBS.

At Step 4, HNBS derives an IMS subscription for the Legacy UE from anHSS, wherein the HSS stores the IP-Address of the HNBS, deletes the MSCas the paging location, and sets the IMS as new paging location in theHLR/HSS. This aspect of the procedure may have the effect that it allowsthe network or network operator to decide whether IMS access will beallowed for a requesting UE. Further, the HLR/HSS is not required tocreate IMS subscriber records for all UEs registered in the CS domain.It may be sufficient to create an IMS record when needed for the firsttime.

At Step 5, the HNBS registers the Legacy UE in the IMS and in theVirtual Channel Connection Access Stratum (VCC-AS) based on the IMSsubscription data. The IP-Address of the HNBS is included in theRegister message. This aspect of the procedure may have the effect thatit is difficult to fake the subscription. For example, network securityis maintained by not configuring the HNBS to generate the IMSsubscription.

At Step 6, the HNBS generates a TMSI for the Legacy UE and transmits theTMSI via a ciphered connection to the Legacy UE. The generated TMSI maybe identical to the P-TMSI received from the SGSN. This aspect of theprocedure may have the effect that the CS-based signaling for MobilityManagement could be offered without requiring a MSC.

As a result of the message sequence of FIG. 4, the Legacy UE canestablish a CS-based connection for a voice call as it would normally.This call is converted by the HNBS into a PS-based call, in someembodiments a VoIP-call, and controlled by the VCC-AS. In someembodiments, the above procedure results in not using any CS-basednetwork elements (e.g., a MSC) in the core network for establishing andmaintaining a call initiated by a Legacy UE. In some embodiments, whenan incoming voice call for the Legacy UE reaches the core network, thecall is transported via PS-based transport means to the HNBS, whereinthe call is converted into a CS-based voice call by the HNBS andtransmitted to the UE.

FIGS. 6A and 6B shows a message sequence chart and network map of acircuit switch user equipment accessing an IP Multimedia Subsystemnetwork via a Home Node Subsystem according to an embodiment.

As shown in FIG. 6A, at Step 1, UE 602 is IMSI attached to the CS-domainvia NodeB 606, RNC 608, and MSC 610. UE 602, from a previous procedure,has obtained and stored a LAI and a TMSI. UE 602 moves, in idle mode insome embodiments, into the coverage area of HNB 612, which transmit adifferent LAI. UE 602 selects HNB 612 and detects that the LAI receivedfrom HNB 612 is different from the stored LAI. Thus, a location updateprocedure is triggered.

At Step 2, UE 602 transmits a location updating request message toHNB-GW 614 via HNB 612. From the perspective of UE 602, the procedure ofFIGS. 6A and 6B, including the location updating request message, isidentical to sending the message to MSC 610. HNB 612 routes to HNB-GW614 the currently assigned TMSI and the LAI received from the “old”NodeB 606.

At Step 3, HNB-GW 614 converts the message into a Location Update andIMS Subscription Request message and transmits it to SGSN 616. That is,an embodiment includes a location update for UE 602 and to obtain an IMSSubscription from HLR/HSS 620. Location Update and IMS SubscriptionRequest message includes the TMSI and LAI obtained by the UE 602 fromthe “old” cell of NodeB 606 and the IP-Address used by HNBS 615.

At Step 4, SGSN 616 detects that the received LAI is different from itsown RAI. SGSN 616 then uses the old LAI to obtain the address of “old”MSC 610 and transmits a Send Parameters message to MSC 610 in order toobtain an identification of UE 602. The Send Parameters message includesthe TMSI of UE 602. MSC 610 sends the corresponding user identity (IMSI)and the security credentials associated with UE 602 back to SGSN 616. Insome embodiments, if no credentials are available from MSC 610, SGSN 616requests them from HLR/HSS 620.

At Step 6, SGSN 616 generates a P-TMSI for UE 602 and stores the P-TMSIand the security credentials associated with UE 602. SGSN 616 thentransmits the security credentials and the P-TMSI to HNBS 615. In someembodiments, the stored security credentials are used when UE 602performs a GPRS-attach in order to use PS-based services in addition tothe CS-services. In such an embodiment, SGSN 616 is prepared to receivean Attach Request message from UE 602.

SGSN 616 will update the location in HLR/HSS 620 and will transmit theP-TMSI to UE 602. Thus, it is not required to derive the IMSI or thesecurity credentials from MSC 610 again. In some embodiments, the storedP-TMSI is used when UE 602 initiatives a location update procedure fromin a different cell (e.g. a macro cell surrounding HNB 612. In such anembodiment, SGSN 616 responses to the requesting MSC or SGSN with theIMSI of UE 602.

At Step 6, SGSN 616 initiates the authentication procedure bytransmitting an Authentication and Ciphering Request message to UE 602.HNB-GW 614 receives this request and forwards it with CS-based transportmeans (e.g., the mobility management protocol layer) to UE 602. UE 602verifies, based on the received data, that the request is trustful andcomputes a result to the challenge. UE 602 transmits the result back toSGSN 616 by transmitting an Authentication and Ciphering Responsemessage. HNB-GW 614 receives this request and forwards it with PS-basedtransport means (e.g., the GPRS mobility management protocol layer) toSGSN 616. SGSN 616 compares the result with the stored data obtainedfrom HLR/HSS 620. If the result matches, UE 602 is authenticated. Thisaspect of the procedure may have the effect that the procedure enablesthe authentication among a CS-based UE and PS-based network entitieswithout a degradation of network security. For example, it would bedifficult to fake the authentication procedure by HNBS 615.

At Step 7, SGSN 616 transmits an Update Location and Proxy IMS IDRequest message to HLR/HSS 620. The message includes the IMSI, theIP-Address of HNBS 615, and an indication that IMS 622 will be used forvoice services. That is, in some embodiments, IMS 622 will replace CSdomain 624 for voice services. HLR/HSS 620 checks, based on the IMSI,whether the UE 602 should get permission to access IMS 622. The decisioncould be based on, for example, a user's contract/tariff agreements. IfIMS 622 access is acceptable and if no IMS data record exists for the UE602, (e.g. because this is the first time the user enters a HNBScoverage area that performs an IMS registration for UE 602) HLR/HSS 620generates an IMPU for UE 602. In some embodiments, HLR/HSS 620 mayinclude the MSISDN or other known IDs of the user and/or UE 602 into theIMPU. In some embodiments, a randomly generated number may be includedinto the IMPU so that it is more difficult to fake an IMPU. HLR/HSS 620updates the record for UE 602 with the received and generatedparameters. HLR/HSS 620 deletes the “connection” to MSC 610, which wasformerly used to page UE 602. HLR/HSS 620 also stores data to indicatethat IMS 622 pages UE 602 and stores the IP-Address of HNBS 615. HLR/HSS620 sends an Update Location ACK and Proxy IMS ID Assignment messageback to SGSN 616.

Some embodiments include Step 7 a. At Step 7 a, HLR/HSS 620 transmits aCancel Location message to old MSC 610. MSC 610 deletes the record andtransmits a Cancel Location Result message back to HLR/HSS 620. In otherembodiments, the deletion may also be performed in MSC 610 when UE 602does not transmit a Location Updating Request message to MSC 610 withina predefined period.

At Step 8, SGSN 616 forwards the IMPU to HNB-GW 614.

As shown in FIG. 6B, at Step 9, HNB-GW 614 operates as an IMS client toIMS 622 and performs all relevant steps to register in the IMS 622 onbehalf of UE 602. HNB-GW 614 transmits a SIP Register message to P-CSCF626. The SIP Register message includes the IP-Address of HNBS 615 andthe IMPU. P-CSCF 626 checks the source IP address against the SIP fieldand forwards the message to I-CSC 628 if both are the same. I-CSCF 628transmits a User Authentication Request message, which includes the IMPUand the IP-Address of HNBS 615, to HLR/HSS 620. HLR/HSS 620 compares thereceived IMPU and IP-Address with the stored parameters and acknowledgesthe authentication to I-CSCF 628 with a User Authentication Answermessage if the received parameters are equal to the stored parameters.IMS nodes (e.g., CSCFs) then execute the register procedures.

At Step 10, I-CSCF 628 sends a SIP REGISTER message to S-CSCF 630.S-CSCF 630 then transmits a Server Assignment-Request message to HLR/HSS620. HLR/HSS 620 stores the received data associated with UE 602 andtransmits a Server Assignment Answer back to S-CSCF 630. In someembodiments, HLR/HSS 620 will use this data to page UE 602 via IMS 622.S-CSCF 630 sends the SIP REGISTER message to VCC-AS 632, which responseswith a 200 OK message back to S-CSCF 630. Registration at VCC-AS 632 isperformed to enable Voice-Call-Continuity when handover to surroundingmacro cells occurs.

At Step 11, S-CSCF 630 transmits a SIP 200 OK message back to HNB-GW614.

At Step 12, HNB-GW 614 receives the SIP 200 OK message. HNB-GW 614 thengenerates a TMSI for UE 602, stores the TMSI associated with UE 602, andtransmits a Location Updating Accept message, which includes the TMSI,to UE 602. The message is encrypted with the security credentialsreceived from SGSN 616. In some embodiments, the generated TMSI may beidentical to the P-TMSI received from SGSN 616. HNB-GW 614 is now ableto translate incoming VCC-calls into a CS call and forwards the CS voicedata to UE 602.

Step 13: The HNB-GW 614 transmits a message to the VCC-AS with thepreferred domain for this UE 602. In various embodiments, the Domain isthe PS-Domain/IMS 622 in case that UE 602 is attached to both domains.The message is transmitted by using http. The address of the VCC-AS maybe obtained by previously received messages from the HLR/HSS or theaddress is preconfigured during set-up of the HNB-GW 614. In case thatthe HNB-GW 614 already set this status for this UE 602, there is no needto transmit this message again.

In alternative embodiments, Step 13 may be omitted if the preferreddomain is already known by the VCC-AS. For example, if the PS-Domain isset by default as the preferred domain after a UE is registered in theIMS or the preferred domain was set formerly by other means (e.g. by theuser), then Step 13 may be omitted.

At Step 14, UE 602 utilizes the TMSI and transmits a TMSI ReallocationComplete message back to HNB-GW 614. This indicates the successfulcompletion of the location updating procedure.

Thus, HNB-GW 614 will translate every CS-signaling on the side of UE 602into SIP/IMS-signaling on NW-side (network-side) and vice versautilizing the established connection towards IMS 622 and emulating anMSC towards UE 602. HNB-GW 614 utilizes the security credentialsreceived by SGSN 616 to encrypt messages transmitted over the air to UE602 and to decrypt messages received over the air from UE 602.

A voice call is established by UE 602 transmitting a Setup message toHNBS 615. This triggers HNBS 615 to set up a SIP Session by transmittingan Invite message to P-CSCF 626. The messages received by HNBS 615during this procedure are translated into CS-based Call Control messagesand transmitted to UE 602 if applicable.

It will be understood that the message sequence chart and network map ofFIGS. 6A and 6B is only one possible message sequence, and that theremay be many variations or additions to the architecture. For example,other embodiments may include UE 602 re-registration IMS 622, or IMS 622re-registration or deregistration UE 602.

In summary, embodiments include a HNBS configured to perform IMS-relatedtasks on behalf of legacy UEs. In some embodiments, a HNBS is configuredto perform a protocol conversion function for received mobilitymanagement messages used by a UE in the CS-Domain (e.g., a locationupdating request). For example, a HNBS may convert a received CS-Domainmobility management message into a messages that will set the IMS as newlocation for paging and will request for an IMS subscription at theHLR/HSS.

In some embodiments, an HNBS is configured to perform a protocolconversion function that is able to receive 3G PS Domain authenticationmessages from the network (e.g. an Authentication and Ciphering Requesttransmitted via the lugs-Interface) and forward these messages withprotocols used in the 3G CS Domain to the UE and vice versa.

In some embodiments, an HNBS is configured to generate a TMSI for a UEthat transmitted a Location Updating Request and transmits the TMSI viaa ciphered connection to the requesting UE.

In some embodiments, an HNBS is configured to set the IMS as thepreferred domain in the VCC-AS for a UE that connects to the HNBS.

The above embodiments are advantageous because they do not require anychanges for legacy UEs. Further, no connection towards an MSC isrequired when a UE connects to an HNBS. Also, in some embodiments, anIMSI is not required to be stored in an HNBS. Therefore, the level ofsecurity is not degraded by the described embodiments.

In some embodiments, an HLR/HSS is configured to receive a request for aIMS Subscription. This request may be combined with a request forlocation update. The formerly stored location (e.g., an MSC) is deleted.A flag to use the IMS for paging and the IP-Address of the HNBS areinserted. If no IMS subscription record exists for a UE, the HLR/HSS isconfigured to create a new record for an IMS subscriber. A response withthe requested IMS Subscription is transmitted to the requesting entity.The HLR/HSS may also reject the request.

The above embodiments are advantageous because it is up to the networkor the Operator to decide whether IMS access will be allowed for a useror UE. The above embodiments are also advantageous because it is notrequired that the HLR/HSS create IMS subscriber records for all UEsregistered in the CS domain. In some embodiments, it is sufficient tocreate such a record when it is needed for the first time.

In some embodiments, an SGSN is configured to transmit securitycredentials for an UE connecting to an HNBS. In some embodiments, uponreceived a update Location and Proxy IMS ID Request message, the SGSN isconfigured to request a temporary IMS Subscription from the HLR/HSS andto transmit the IP-address of the HNBS to the HLR/HSS. In someembodiments, the SGSN is configured to receive an Update Location ACKand Proxy IMS ID Assignment message from a HLR/HSS and forward thereceived IMS subscription towards the requesting entity.

The above embodiments are advantageous because they may utilize existingrouting functions of the core network.

FIGS. 7A-7D show communication method embodiments. In FIG. 7A, method700 begins at 702 with receiving, by a home base station system, aunique user identifier, for example a TMSI from a UE. At 704, anInternet Protocol multimedia subscription request message comprising theunique user identifier and an information request message is generatedby a home base station system. The information request message requestsan Internet Protocol multimedia subscription for the user identified bythe unique user identifier generating. At 706, the generated InternetProtocol multimedia subscription request message is transmitted by thehome base station system to a user database.

In FIG. 7B, method 710 begins at 712 with receiving by a user database,for example an HLR/HSS, the Internet Protocol multimedia subscriptionrequest message. At 714, the user database generates an InternetProtocol multimedia subscription for the user identified by the uniqueuser identifier in the received Internet Protocol multimediasubscription request message. At 716, the user database transmits theInternet Protocol multimedia subscription to the home base stationsystem.

In FIG. 7C, method 720 begins at 722 with a home base station system,receiving a circuit-switched based mobility management message. At 724,the home base station generates a packet-switched based attach requestmessage to attach to a packet-switched domain.

In FIG. 7D, method 730 begins at 732 with a home base station systemreceiving a circuit-switched based message including a user identifier.At 734, the home base station generates a packet-switched based messageto request security-related information associated with the receiveduser identifier. At 736, the home base station system receives apacket-switched based authentication request message. At 738, the homebase station system generates a circuit-switched based message torequest authentication of a communication device associated with theuser identified by the user identifier. At 740, the home base stationsystem transmits the circuit-switched based message to the communicationdevice.

FIG. 8 shows block diagrams of an architecture for HNB 800. HNB 800includes a processor 802, memory 804, a radio module 806, a powercontroller 807, and a network interface 208, connected by a bus 810. Insome embodiments, the memory 804 may include random access memory 812,such as conventional DRAM, and non-volatile memory 814, such asconventional flash memory, for storing the firmware that operates theHNB 800, as well as other parameters and settings that should beretained by the HNB 800.

The radio module 806 may include an antenna 816, which is used forcommunication wirelessly with one or more UEs, such as mobiletelephones. The network interface 808 connects the HNB 800 to HNB-GW(now shown), and may be a conventional wired network interface, such asa DSL interface, an Ethernet interface, or a USB interface that connectsto an external computer or network interface device for connection toHNB-GW (now shown). Alternatively, the network interface 808 may be awireless network interface that communicates with HNB-GW via a wirelesslocal-area network, a wireless metropolitan area network or a wirelesswide area network.

The HNB 800 may be housed in a compact, portable housing (not shown),and may be powered by a conventional home power connection (not shown),via the network interface 808 (e.g., power via a USB connection or powerover Ethernet), or by other known methods of powering an electronicdevice. In some embodiments, the HNB base station 800 may include abackup power source 818, such as a battery (which may be a rechargeablebattery) connected to the power controller 807, which may provide powerfor the HNB 800 to continue operation for a limited duration in theevent of a power loss, such as may occur if the HNB 800 is unplugged orswitched off.

It will be understood that the architecture shown in FIG. 8 is only onepossible architecture for the HNB 800, and that there may be manyvariations or additions to the architecture. For example, the HNB 800may include I/O devices, such as a display (not shown), a smart cardinterface and a smart card (not shown), to verify that the HNB isauthorized for operation, or a variety of indicator lights or LEDs (notshown), to indicate the current status of the HNB 800.

While the invention has been particularly shown and described withreference to specific embodiments, it should be understood by thoseskilled in the art that various changes in form and detail may be madetherein without departing from the spirit and scope of the invention asdefined by the appended claims. The scope of the invention is thusindicated by the appended claims and all changes which come within themeaning and range of equivalency of the claims are therefore intended tobe embraced.

Those of skill in the art would appreciate that the various illustrativelogical blocks, modules, circuits, and algorithm steps described inconnection with the disclosure herein may be implemented as electronichardware, computer software, or combinations of both. To clearlyillustrate this interchangeability of hardware and software, variousillustrative components, blocks, modules, circuits, and steps have beendescribed above generally in terms of their functionality. Whether suchfunctionality is implemented as hardware or software depends upon theparticular application and design constraints imposed on the overallsystem. Skilled artisans may implement the described functionality invarying ways for each particular application, but such implementationdecisions should not be interpreted as causing a departure from thescope of the present disclosure.

For example, the various illustrative logical blocks, modules, andcircuits described in connection with the disclosure herein may beimplemented or performed with a general-purpose processor, a digitalsignal processor (DSP), an application specific integrated circuit(ASIC), a field programmable gate array (FPGA) or other programmablelogic device, discrete gate or transistor logic, discrete hardwarecomponents, or any combination thereof designed to perform the functionsdescribed herein. A general-purpose processor may be a microprocessor,but in the alternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

The steps of a method or algorithm described in connection with thedisclosure herein may be embodied directly in hardware, in a softwaremodule executed by a processor, or in a combination of the two. Asoftware module may reside in RAM memory, flash memory, ROM memory,EPROM memory, EEPROM memory, registers, hard disk, a removable disk, aCD-ROM, or any other form of storage medium known in the art. Anexemplary storage medium is coupled to the processor such that theprocessor can read information from, and write information to, thestorage medium. In the alternative, the storage medium may be integralto the processor. The processor and the storage medium may reside in anASIC. The ASIC may reside in a user terminal. In the alternative, theprocessor and the storage medium may reside as discrete components in auser terminal.

In one or more exemplary designs, the functions described may beimplemented in hardware, software, firmware, or any combination thereof.If implemented in software, the functions may be stored on ortransmitted over as one or more instructions or code on acomputer-readable medium. Computer-readable media includes both computerstorage media and communication media including any medium thatfacilitates transfer of a computer program from one place to another. Astorage media may be any available media that can be accessed by ageneral purpose or special purpose computer. By way of example, and notlimitation, such computer-readable media can comprise RAM, ROM, EEPROM,CD-ROM or other optical disk storage, magnetic disk storage or othermagnetic storage devices, or any other medium that can be used to carryor store desired program code means in the form of instructions or datastructures and that can be accessed by a general-purpose orspecial-purpose computer, or a general-purpose or special-purposeprocessor.

What is claimed is:
 1. A home base station subsystem, comprising: amessage generator configured to generate an Internet Protocol multimediasubscription request message comprising a unique user identifier and aninformation request message, the information request message requestingan Internet Protocol multimedia subscription for the user identified bythe unique user identifier; and a transmitter configured to transmit thegenerated Internet Protocol multimedia subscription request message to auser database; wherein the message generator is configured to generatethe Internet Protocol multimedia subscription request message furthercomprising a unique home base station subsystem identifier.
 2. A homebase station subsystem, comprising: a message generator configured togenerate an Internet Protocol multimedia subscription request messagecomprising a unique user identifier and an information request message,the information request message requesting an Internet Protocolmultimedia subscription for the user identified by the unique useridentifier; and a transmitter configured to transmit the generatedInternet Protocol multimedia subscription request message to a userdatabase; wherein the message generator is configured to generate theInternet Protocol multimedia subscription request message furthercomprising a Temporary Mobile Station Identity and a home base stationsubsystem Internet Protocol address.
 3. A home base station subsystem,comprising: a message generator configured to generate an InternetProtocol multimedia subscription request message comprising a temporaryunique user identifier in a circuit switched domain received from a userand an information request message, the information request messagerequesting an Internet Protocol multimedia subscription for the useridentified by the unique user identifier; and a transmitter configuredto transmit the generated Internet Protocol multimedia subscriptionrequest message to a user database, wherein the message generator isconfigured to generate the Internet Protocol multimedia subscriptionrequest message further comprising a unique home base station subsystemidentifier.
 4. The home base station subsystem of claim 3, wherein thetransmitter is configured to transmit the generated Internet Protocolmultimedia subscription request message to a home location register. 5.A home base station subsystem, comprising: a message generatorconfigured to generate an Internet Protocol multimedia subscriptionrequest message comprising a temporary unique user identifier in acircuit switched domain received from a user and an information requestmessage, the information request message requesting an Internet Protocolmultimedia subscription for the user identified by the unique useridentifier; and a transmitter configured to transmit the generatedInternet Protocol multimedia subscription request message to a userdatabase, wherein the message generator is configured to generate theInternet Protocol multimedia subscription request message furthercomprising a Temporary Mobile Station Identity and a home base stationsubsystem Internet Protocol address.
 6. The home base station subsystemof claim 5, wherein the transmitter is configured to transmit thegenerated Internet Protocol multimedia subscription request message to ahome location register.
 7. A user database system comprising: a receiverconfigured to receive an Internet Protocol multimedia subscriptionrequest message comprising a unique user identifier and an informationrequest message, the information request message requesting an InternetProtocol multimedia subscription for the user identified by the uniqueuser identifier; an Internet Protocol multimedia subscription generatorconfigured to generate an Internet Protocol multimedia subscription forthe user identified by the unique user identifier in the receivedInternet Protocol multimedia subscription request message; and atransmitter configured to transmit the Internet Protocol multimediasubscription to a home base station subsystem, wherein the user databasesystem comprises a home location register.
 8. The user database systemof claim 7, wherein the receiver is configured to receive an indicatorthat the Internet Protocol multimedia subscription will be used forvoice services.
 9. The user database system of claim 7, wherein theInternet Protocol multimedia subscription generator is configured togenerate an Internet Protocol multimedia subscription comprising anInternet Protocol Multimedia Public Identity.
 10. The user databasesystem of claim 9, wherein the Internet Protocol multimedia subscriptiongenerator is configured to generate the Internet Protocol multimediasubscription further comprising a generated random number.
 11. The userdatabase system of claim 7 further comprising a subscription moduleconfigured to determine whether the Internet Protocol multimediasubscription is allowed for the user identified by the unique useridentifier.
 12. A user database system comprising: a receiver configuredto receive an Internet Protocol multimedia subscription request messagecomprising a unique user identifier and an information request message,the information request message requesting an Internet Protocolmultimedia subscription for the user identified by the unique useridentifier; an Internet Protocol multimedia subscription generatorconfigured to generate an Internet Protocol multimedia subscription forthe user identified by the unique user identifier in the receivedInternet Protocol multimedia subscription request message; and atransmitter configured to transmit the Internet Protocol multimediasubscription to a home base station subsystem, wherein the receiver isconfigured to receive the Internet Protocol multimedia subscriptionrequest message further comprising a unique home base station subsystemidentifier.
 13. The user database system of claim 12, wherein thereceiver is configured to receive an indicator that the InternetProtocol multimedia subscription will be used for voice services. 14.The user database system of claim 12, wherein the Internet Protocolmultimedia subscription generator is configured to generate an InternetProtocol multimedia subscription comprising an Internet ProtocolMultimedia Public Identity.
 15. The user database system of claim 14,wherein the Internet Protocol multimedia subscription generator isconfigured to generate the Internet Protocol multimedia subscriptionfurther comprising a generated random number.
 16. The user databasesystem of claim 12 further comprising a subscription module configuredto determine whether the Internet Protocol multimedia subscription isallowed for the user identified by the unique user identifier.
 17. Auser database system comprising: a receiver configured to receive anInternet Protocol multimedia subscription request message comprising aunique user identifier and an information request message, theinformation request message requesting an Internet Protocol multimediasubscription for the user identified by the unique user identifier; anInternet Protocol multimedia subscription generator configured togenerate an Internet Protocol multimedia subscription for the useridentified by the unique user identifier in the received InternetProtocol multimedia subscription request message; and a transmitterconfigured to transmit the Internet Protocol multimedia subscription toa home base station subsystem, wherein the Internet Protocol multimediasubscription generator is configured to generate an Internet Protocolmultimedia subscription comprising an Internet Protocol MultimediaPublic Identity, wherein the Internet Protocol multimedia subscriptiongenerator is configured to generate the Internet Protocol multimediasubscription further comprising a generated random number, and whereinthe Internet Protocol multimedia subscription generator is configured togenerate the Internet Protocol multimedia subscription furthercomprising a second unique user identifier.
 18. A user database systemcomprising: a receiver configured to receive an Internet Protocolmultimedia subscription request message comprising a unique useridentifier and an information request message, the information requestmessage requesting an Internet Protocol multimedia subscription for theuser identified by the unique user identifier; an Internet Protocolmultimedia subscription generator configured to generate an InternetProtocol multimedia subscription for the user identified by the uniqueuser identifier in the received Internet Protocol multimediasubscription request message; and a transmitter configured to transmitthe Internet Protocol multimedia subscription to a home base stationsubsystem, wherein the user database system is further configured to setan Internet Protocol Multimedia Subsystem as a paging location for theuser identified by the unique user identifier.